The scope of this specification covers all the provisions necessary to enable communication between airborne and ground applications.

Various types of communication can take place between aircraft and ground:

1. ACARS system traditionally enables the exchange of messages. These messages can be exchanged asynchronously or in a synchronous way (see note below)

2. Most EFB type applications also use messages to communicate (e.g., electronic Flight Folder (eFF), Weight and Balance Application (WBA))

3. EFB applications will need to be able to use other types of communications (transactional communications, such as database access, web access, etc.) that do not involve individual messages exchanges.

This specification addresses the first 2 types of communications. When the need for standardization arises, other types of exchanges than message exchanges will be added.

Depending on the type of exchanges, asynchronous or synchronous message exchanges are addressed in this document.

Note: ‘Asynchronous’ communications means that there is no need for the end applications to be active and ready to communicate during the communication. Typically, an application can send a message to a ground message server, and the receiving application can retrieve it when it gets activated.

‘Synchronous’ communications are used here to depict exchanges where both end applications are active and communicating, allowing real bidirectional exchanges.

Transport technologies (especially TCP/IP based networks) are evolving rapidly; therefore the present document segregates application level functionalities from transport functionalities.